The present invention relates to a method and a regenerative separation device, in particular a filter device, for separating impurities from process exhaust air, for example for separating organic solvents from solvent-containing process exhaust air, for example for use in an industrial surface treatment plant.
Cleaning of process exhaust air having low concentration or loading of at least one combustible subcomponent, in particular of organic solvents, such as paint exhaust air such as it is incurred, for example, in painting plants of vehicle bodies, is for example carried out by means of a method for up-concentrating. Here, the volatile organic solvents are physically attached (adsorption, absorption) to a separation unit, in particular a filter of a separating device. This process can be reversed (desorption) by increasing the temperature of the filter.
For the desorption process, for example, hot air of 140 to 450° C. having a low flow rate is used. The hot air exiting the separating device, in particular filtering device, after passing through the separating unit, in particular the filter, is also referred to as a concentrate air. The concentration of solvent in the concentrate air increases in the same proportion as the flow rate is reduced, compared to the process exhaust air. With conventional systems, increases of concentration in the concentrate air in a ratio of 2:1 to 20:1 in relation to the process exhaust air can be achieved. The limits of this up-concentration result from reaching a lower explosive limit and exceeding the ignition temperature. The concentrate air finally can be fed to a cleaning device to extract or recover the solvents.
Such a method for separating organic solvents from solvent-containing process exhaust air is disclosed for example in DE 39 35 094 C2. In this conventional method, a continuously operated separating device, in particular filtering device, comprising separation unit, in particular a filter, designed as a rotor is used whose end faces are continuously loaded by process exhaust air and hot air. Here, the separating device, in particular filtering device, is divided into a sector-shaped separation zone and a sector-shaped regeneration zone which are passed by the rotating separation unit, in particular the rotating filter, continuously one after the other.
As the region of the filter entering the regeneration zone initially is still on the temperature level of the attaching process of, for example, about 10 to 60° C., and has to be heated by the hot air on, for example, about 140 to 450° C., the temperatures of the filter are not sufficient to desorb the attached solvents in the first subportion of the filter, in a first phase of the regeneration process. This may result in that the solvent concentration in the concentrate air and the efficiency of the downstream cleaning device are insufficient or reduced.
Therefore, it is an object of the invention to provide a method and a regenerative separating device, in particular filtering device, for separating impurities from process exhaust air which enable greater efficiency.